1. Field of the Invention
This disclosure relates to a touch sensing panel and more particularly to a capacitive touch sensing panel that is capable of improving performance of touch precision of corners part or edges thereof.
2. Discussion of the Related Art
In recent years, various input devices such as a keyboard, a mouse, a joystick and a digitizer are used for constructing interface between users and home appliances or information telecommunication devices. However, when a user makes use of the input devices, user's dissatisfaction increases because the user is required to know how to use the input devices and the input devices occupy space. Therefore, a convenient and simple input device that can reduce erroneous operation is required. According to the requirement, there proposed a touch sensor that can input information by directly contacting a screen with a user's finger or a pen.
Touch sensing panels are classified into a resistive type, a capacitive type, an electromagnetic type according to a detection method of a touched portion. The resistive type touch sensing panel determines a touched position by a voltage gradient according to a change of resistance in a state that a DC voltage is applied to metal electrodes formed on an upper plate or a lower plate. The capacitive type touch sensing panel senses a touched position according to a difference in capacitance created in an upper or lower plate when the user physically contacts with a conductive film formed on the upper or lower plate. The electromagnetic type touch sensing panel detects a touched portion by reading an LC value induced as an electromagnetic pen touches a conductive film. In addition to above-mentioned type touch sensing panels, optical type and ultrasonic type touch sensing panels are known.
Among the above-mentioned touch sensing panels, the capacitive type touch sensing panel is classified into a self capacitive type touch sensing panel and a mutual capacitive type touch sensing panel. The self capacitive type touch sensing panel has a construction in which a plurality of independent patterns are formed in touch area. In the self capacitive type touch sensing panel, touched positions are detected by measuring change of capacitances of the independent patterns. The mutual capacitive type touch sensing panel has a matrix construction in which first electrode patterns (e.g., touch driving electrodes) arranged in an x-axis direction cross over second electrode patterns (e.g., touch sensing electrodes) arranged in a y-axis direction. In the mutual capacitive type touch screen panel, touch positions are detected by measuring changes of capacitances appeared to sensing nodes which are defined by cross points of the touch driving and sensing electrodes through the touch sensing electrodes after supplying a driving voltage to the touch driving electrodes.
Hereinafter, a related art capacitive type touch sensing panel for a display device will be described with reference to FIGS. 1A and 1B. FIG. 1A is a planar view illustrating a related art capacitive type touch sensing panel for a display device, and FIG. 1B is conceptive view illustrating sensing nodes formed on the touch sensing panel shown in FIG. 1A.
Referring to FIGS. 1A and 1B, the capacitive type touch sensing panel includes a touch electrode forming area TA, an active area AA, a routing wire forming area RA and a pad forming area PA. Touch electrodes having touch driving electrodes and touch sensing electrodes are formed on the touch electrode forming area TA. The active area AA is an area corresponding to area on which data of a display device are displayed. Routing wires are formed on the routing wire forming area RA to be connected to the touch electrodes. Routing pads are formed on the pad forming area PA to connect the routing wires to signal lines of a touch processor (not shown).
The touch electrode forming area TA includes a plurality of first touch electrode serials TS1 to TS5 arranged in parallel in a first direction (e.g. x axis direction), and a plurality of second touch electrode serials RS1 to RS5 arranged in parallel in a second direction (e.g. y axis direction) crossing over the first direction. Positions where the plurality of first touch electrode serials TS1 to TS5 cross over the plurality of second touch electrode serials RS1 to RS6 are referred to as sensing nodes n11 to n56. The plurality of first touch electrode serials TS1 to TS5 cross over the plurality of second touch electrode serials RS1 to RS6 with an insulation layer (not shown) therebetween not to contact with each other at the sensing nodes n11 to n56.
The routing wire forming area RA is disposed outside the touch electrode forming area RA, and includes a plurality of first routing wires TW1 to TW5 connected to the plurality of first touch electrode serials TS1 to TS5, respectively and a plurality of second routing wires RW1 to RW6 connected to the plurality of second touch electrode serials RS1 to RS6, respectively.
The pad forming area PA includes a plurality of first routing pads TP1 to TP5 connected to the plurality of first routing wires TW1 to TW5, respectively and a plurality of second routing pads RP1 to RP6 connected to the plurality of second routing wire RW1 to RW6, respectively.
The mentioned above capacitive type touch sensing panel is a device which detects touch positions by finding changes of capacitances at the sensing nodes n11 to n56 adjacent to the touch positions when an user touches the touch sensing panel with fingers or a conductive metal such as a stylus pen. As thus, the sensing nodes n11 to n56 are used as a reference to trace touch positions. Accordingly, the touch electrode forming area TA is set to have an area larger than the active area AA so that it is possible to touch an entire area of the active area AA corresponding to a display area of the display device. However touches are not exactly performed on the sensing nodes n11 to n56 but mostly performed on positions between the sensing nodes n11 to n56. Accordingly, the touch sensing panel detects touch positions by processing data collected from the sensing nodes adjacent to the touch positions.
FIG. 2 is a planar view illustrating sensing nodes of the related art touch sensing panel usable according to touch positions. In FIG. 2, symbols A, B and C indicate touch positions in an active area of touch sensing panel.
Referring to FIG. 2, in case that a touch is performed at the touch position A in the active area AA, it is possible to use nine sensing nodes n34, n35, n36, n44, n45, n46, n54, n55 and n56 adjacent to the touch position A to obtain the touch position A. Also, in case that a touch is performed at the touch position B including a sensing node n41 at one edge of the active area AA, it is possible to use six sensing nodes n31, n32, n41, n42, n51 and n52 adjacent to the touch position B to obtain the touch position B. However, in case that a touch is performed at the touch position B′ having no sensing node at the one edge of the active area AA, it is possible to use only two sensing nodes n31 and n41 adjacent to the touch position B′ to obtain the touch position B′. Also, in case that a touch is performed at a touch position C including a sensing node n11 at one corner of the active area AA, it is possible to use four sensing nodes n11, n12, n21 and n22 adjacent to the touch position C to obtain the touch position C. However, in case that a touch is performed at the touch position C′ having no sensing node at the one corner of the active area AA, it is possible to use only one sensing node n11 adjacent to the touch position C′ to obtain the touch position C′.
As thus, in case that a touch is performed at inside edges or corners of the active area AA, it is possible to use many sensing nodes adjacent to the touch position, thereby capable of obtaining the touch positions exactly. However, in case that a touch is performed at edges or corners of the active area AA, it is possible to use a few sensing nodes adjacent to the touch position. The touch position obtained by using the few sensing nodes leads a real touch position to an erroneous touch position which is biased to inner side of the active area AA. In particular, in case that a touch is performed at edges or corners of the active area AA having no sensing node, it is impossible to obtain an exact touch position because it is possible to use only one or two sensing nodes.
Accordingly, it is required to prevent erroneous detection of the touch position due to insufficiency of sensing nodes when a touch is performed at edges or corners of the active area AA having no sensing node.
Accordingly, the requirement of a touch sensing panel capable of solving the problems of the related art touch sensing panel was on the rise.